The oxygen abundance in the H II regions of the spiral galaxy M101 determined from the Sloan Digital Sky Survey spectra

2007 ◽  
Vol 23 (4) ◽  
pp. 163-170 ◽  
Author(s):  
Yu. S. Sholudchenko ◽  
I. Yu. Izotova ◽  
L. S. Pilyugin
Keyword(s):  
Spiral Galaxy ◽  
Sloan Digital Sky Survey ◽  
H Ii Regions ◽  
Oxygen Abundance ◽  
Sky Survey

scholarly journals Surface Photometry of Spiral Galaxy NGC 5005 and Elliptical Galaxy NGC 4278

2018 ◽  
Vol 15 (3) ◽  
pp. 314-323
Author(s):  
Baghdad Science Journal
Keyword(s):  
Spiral Galaxy ◽  
Surface Brightness ◽  
Elliptical Galaxy ◽  
Position Angle ◽  
Sloan Digital Sky Survey ◽  
Surface Photometry ◽  
Contour Maps ◽  
Sky Survey ◽  
Flat Field ◽  
The Galaxy

Two galaxies have been chosen, spiral galaxy NGC 5005 and elliptical galaxy NGC 4278 to study their photometric properties by using surface photometric techniques with griz-Filters. Observations are obtained from the Sloan Digital Sky Survey (SDSS). The data reduction of all images have done, like bias and flat field, by SDSS pipeline. The overall structure of the two galaxies (a bulge, a disk), together with isophotal contour maps, surface brightness profiles and a bulge/disk decomposition of the galaxy images were performed, although the disk position angle, ellipticity and inclination of the galaxies have been estimated.

scholarly journals The Oxygen Abundance of Nearby Galaxies from Sloan Digital Sky Survey Spectra

2007 ◽  
Vol 669 (1) ◽  
pp. 299-314 ◽  
Author(s):  
Leonid S. Pilyugin ◽  
Trinh X. Thuan
Keyword(s):  
Sloan Digital Sky Survey ◽  
Oxygen Abundance ◽  
Sky Survey ◽  
Nearby Galaxies

scholarly journals Chemical abundances of Seyfert 2 AGNs – I. Comparing oxygen abundances from distinct methods using SDSS

2019 ◽  
Vol 492 (1) ◽  
pp. 468-479 ◽  
Author(s):  
O L Dors ◽  
P Freitas-Lemes ◽  
E B Amôres ◽  
E Pérez-Montero ◽  
M V Cardaci ◽  
...  
Keyword(s):  
Sloan Digital Sky Survey ◽  
Strong Line ◽  
Host Galaxies ◽  
Chemical Abundances ◽  
Oxygen Abundance ◽  
Line Intensities ◽  
Sky Survey ◽  
Direct Measurements ◽  
Low Metallicity ◽  
Semi Empirical

ABSTRACT We compare the oxygen abundance (O/H) of the narrow-line regions (NLRs) of Seyfert 2 AGNs obtained through strong-line methods and from direct measurements of the electron temperature (Te-method). The aim of this study is to explore the effects of the use of distinct methods on the range of metallicity and on the mass–metallicity relation of active galactic nuclei (AGNs) at low redshifts (z ≲ 0.4). We used the Sloan Digital Sky Survey (SDSS) and NASA/IPAC Extragalactic Database (NED) to selected optical (3000 < λ(Å) < 7000) emission line intensities of 463 confirmed Seyfert 2 AGNs. The oxygen abundances of the NLRs were estimated using the theoretical Storchi-Bergmann et al. calibrations, the semi-empirical N2O2 calibration, the Bayesian H  ii-Chi-mistry code and the Te-method. We found that the oxygen abundance estimations via the strong-line methods differ from each other up to ∼0.8 dex, with the largest discrepancies in the low-metallicity regime ($\rm 12+\log (O/H) \: \lesssim \: 8.5$). We confirmed that the Te-method underestimates the oxygen abundance in NLRs, producing unreal subsolar values. We did not find any correlation between the stellar mass of the host galaxies and the metallicity of their AGNs. This result is independent of the method used to estimate Z.

scholarly journals Oxygen abundance in the Sloan Digital Sky Survey

2006 ◽  
Vol 453 (2) ◽  
pp. 487-492 ◽  
Author(s):  
F. Shi ◽  
X. Kong ◽  
F. Z. Cheng
Keyword(s):  
Sloan Digital Sky Survey ◽  
Oxygen Abundance ◽  
Sky Survey

scholarly journals SpArcFiRe: Enhancing Spiral Galaxy Recognition Using Arm Analysis and Random Forests

Galaxies ◽  
2018 ◽  
Vol 6 (3) ◽  
pp. 95 ◽  
Author(s):  
Pedro Silva ◽  
Leon Cao ◽  
Wayne Hayes
Keyword(s):  
Random Forest ◽  
Spiral Galaxy ◽  
Sloan Digital Sky Survey ◽  
Box Models ◽  
Sky Survey ◽  
Human Volunteers ◽  
Automated Quantification ◽  
Post Hoc ◽  
Black Box Models ◽  
Galaxy Morphology

Automated quantification of galaxy morphology is necessary because the size of upcoming sky surveys will overwhelm human volunteers. Existing classification schemes are inadequate because (a) their uncertainty increases near the boundary of classes and astronomers need more control over these uncertainties; (b) galaxy morphology is continuous rather than discrete; and (c) sometimes we need to know not only the type of an object, but whether a particular image of the object exhibits visible structure. We propose that regression is better suited to these tasks than classification, and focus specifically on determining the extent to which an image of a spiral galaxy exhibits visible spiral structure. We use the human vote distributions from Galaxy Zoo 1 (GZ1) to train a random forest of decision trees to reproduce the fraction of GZ1 humans who vote for the “Spiral” class. We prefer the random forest model over other black box models like neural networks because it allows us to trace post hoc the precise reasoning behind the regression of each image. Finally, we demonstrate that using features from SpArcFiRe—a code designed to isolate and quantify arm structure in spiral galaxies—improves regression results over and above using traditional features alone, across a sample of 470,000 galaxies from the Sloan Digital Sky Survey.

scholarly journals A reassessment of strong line metallicity conversions in the machine learning era

2021 ◽  
Vol 503 (1) ◽  
pp. 1082-1095
Author(s):  
Hossen Teimoorinia ◽  
Mansoureh Jalilkhany ◽  
Jillian M Scudder ◽  
Jaclyn Jensen ◽  
Sara L Ellison
Keyword(s):  
Machine Learning ◽  
Sloan Digital Sky Survey ◽  
Strong Line ◽  
H Ii Regions ◽  
Polynomial Coefficients ◽  
Sky Survey ◽  
Wide Range ◽  
Machine Learning Approach ◽  
Data Release ◽  
Linear Behaviour

ABSTRACT Strong line metallicity calibrations are widely used to determine the gas phase metallicities of individual H ii regions and entire galaxies. Over a decade ago, based on the Sloan Digital Sky Survey Data Release 4, Kewley & Ellison published the coefficients of third-order polynomials that can be used to convert between different strong line metallicity calibrations for global galaxy spectra. Here, we update the work of Kewley & Ellison in three ways. First, by using a newer data release, we approximately double the number of galaxies used in polynomial fits, providing statistically improved polynomial coefficients. Second, we include in the calibration suite five additional metallicity diagnostics that have been proposed in the last decade and were not included by Kewley & Ellison. Finally, we develop a new machine learning approach for converting between metallicity calibrations. The random forest (RF) algorithm is non-parametric and therefore more flexible than polynomial conversions, due to its ability to capture non-linear behaviour in the data. The RF method yields the same accuracy as the (updated) polynomial conversions, but has the significant advantage that a single model can be applied over a wide range of metallicities, without the need to distinguish upper and lower branches in R23 calibrations. The trained RF is made publicly available for use in the community.

scholarly journals A new determination of the primordial helium abundance using the analyses of H ii region spectra from SDSS

2021 ◽  
Vol 502 (2) ◽  
pp. 3045-3056
Author(s):  
O A Kurichin ◽  
P A Kislitsyn ◽  
V V Klimenko ◽  
S A Balashev ◽  
A V Ivanchik
Keyword(s):  
Sloan Digital Sky Survey ◽  
H Ii Regions ◽  
Helium Abundance ◽  
Physical Conditions ◽  
Sky Survey ◽  
H Ii Region ◽  
Standard Cosmological Model ◽  
Primordial Helium ◽  
Good Agreement

ABSTRACT The precision measurement of the primordial helium abundance Yp is a powerful probe of the early Universe. The most common way to determine Yp is the analyses of observations of metal-poor H ii regions found in blue compact dwarf galaxies. We present the spectroscopic sample of 100 H ii regions collected from the Sloan Digital Sky Survey. The final analysed sample consists of our sample and HeBCD data base from Izotov et al. (2007). We use a self-consistent procedure to determine physical conditions, current helium abundances, and metallicities of the H ii regions. From a regression to zero metallicity, we have obtained Yp = 0.2462 ± 0.0022, which is one of the most stringent constraints obtained with such methods up to date and is in a good agreement with the Planck result $Y_{\rm p}^{\it {\mathrm{ Planck}}} = 0.2471 \pm 0.0003$. Using the determined value of Yp and the primordial deuterium abundance taken from Particle Data Group (Zyla et al. 2020) we put a constraint on the effective number of neutrino species Neff = 2.95 ± 0.16, which is consistent with the Planck one Neff = 2.99 ± 0.17. Further increase of statistics potentially allows us to achieve Planck accuracy, which in turn will become a powerful tool for studying the self-consistency of the standard cosmological model and/or physics beyond.

scholarly journals Chemical abundances in active galaxies

2020 ◽  
Vol 496 (2) ◽  
pp. 2191-2203 ◽  
Author(s):  
Sophia R Flury ◽  
Edward C Moran
Keyword(s):  
Direct Method ◽  
Flux Ratio ◽  
Single Equation ◽  
Sloan Digital Sky Survey ◽  
H Ii Regions ◽  
Chemical Abundances ◽  
Temperature Relation ◽  
Oxygen Abundance ◽  
Star Forming ◽  
Liner Galaxies

ABSTRACT The Sloan Digital Sky Survey (SDSS) has proved to be a powerful resource for understanding the physical properties and chemical composition of star-forming galaxies in the local Universe. The SDSS population of active galactic nuclei (AGNs) remains as of yet less explored in this capacity. To extend the rigorous study of H ii regions in the SDSS to AGNs, we adapt methods for computing direct-method chemical abundances for application to the narrow-line regions (NLR) of AGNs. By accounting for triply ionized oxygen, we are able to more completely estimate the total oxygen abundance. We find a strong correlation between electron temperature and oxygen abundance due to collisional cooling by metals. Furthermore, we find that nitrogen and oxygen abundances in AGNs are strongly correlated. From the metal–temperature relation and the coupling of nitrogen and oxygen abundances, we develop a new, empirically and physically motivated method for determining chemical abundances from the strong emission lines commonly employed in flux-ratio diagnostic diagrams (BPT diagrams). Our approach, which for AGNs reduces to a single equation based on the BPT line ratios, consistently recovers direct-method abundances over a 1.5 dex range in oxygen abundance with an rms uncertainty of 0.18 dex. We have determined metallicities for thousands of AGNs in the SDSS, and in the process have discovered an ionization-related discriminator for Seyfert and LINER galaxies.

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